I don't know what you mean by unknown factor but a quotient is the answer of a division problem
The answer is c because the plot begins with 4
Given problem;
A = 4 π R²
To solve for R, we have to make it the subject of the expression.
Since
A = 4 π R² , follow these steps to find R;
Multiply both sides by
A x
=
x 4 π R²
= R²
Then find the square root of both sides
√R² =
R = 
The solution is 
Please help and I will help u
The midpoint is (7,4.75) so the y-coordinate should be y=4.75. I hope that helps